Asbignob



(No Model.)

A. B. DOLBEAR.

MODE 0? ELECTRIC COMMUNICATION.

No. 350,299. Patented Oct. 5, 1886.

UNITED STATES PATENT OFFICE.

AMOS EMERSON DOLBEAR, OF SOMERVILLE, MASSACHUSETTS, ASBIGNOR, BY

MESNE ASSIGNMENTS, TO THE DQLBEAR ELECTRIC TELEPHONE COM- PANY, OF NEW JERSEY.

MODE OF ELECTRIC GOMMUNKEATION.

IPIIGII'IOL'IIOR icnnlngpart'ci Letters la'tsnt 1| 0. 880,399. dated October 5, 1886.

My invention relates to establishing electric communication between two or more places without the use of a wire or other like conduster; and it consists-in connecting the transmitting-instrument with a tialof which is considerab y above the non mal, and the receiving-instrument with a gzlound the potential of whichis considerably" ow the normal, the result being that an impulse from the transmitter suihcient to cause 4 the receiver to give intelligible signals is transmitted through the earth without the need of any circuit, such as has heretoforebeen la di A ts l( n e agram, repruen onepaoe, say Tnitdgncggega) and B a distant place, (say my 0 is a wire leading into the ground atA, and D a wire leading into the ground at B.- G is a secondary coil, one convolution of which is cut, the ends thus formed being connected with the poles of the battery f which has .a number of cells suificient to establish in the wire 0, which is connected with one terminal of the secondary coil G, an electro-motive force of, say, onehundre'd volts. G in this instance also represents an indnctiowcoil, T being a michrophone-transmitter, f its pri-i mary circuit, and 1" its henna-that, iii, the battery f not only furnishes e current for 4a the primary oircu t, but also charges or electrifies the secondary coil G and its terminals 0 and H.

Now, if words be spoken in proximity to transmitter T, the vibration of its diaphragm will disturb the electric condition of the coil G, and thereby vary the potential of the ground at A, and the variations of the tential at A. will cause correspondin v'aria ons'oi' the potential of the ground at and the receiver R round the potenfer to charge all these condensers, as it Serial No. 80,284. (No model.)

at B will reproduce the words spoken in prox- 5o now say.

'Ihere are various well-known ways of elec trii'ying the wire 0 to a positive otential far in excess of a hundred-volts an the wire D to a negative potential farin excess of a hnn- 6 dred volts.

In t1tlhe dialgram, g represenlt ers, econ enser ng ropery a I to in the desired efi'eot. 'Fhe condensers H an H are not essential, but are of someiben- 5 eilt; nor is the condenser H. eueutid when the secondary G is otherwise charged. I re;

0 prime imsortance to keep the grounds of wiresCan' D tigpositelyelsctrifiedgnd while, 7 us is obvious, s may be done by either the bobatteritl1 es or the con ensers; I prei'erto v The main dimculty in utilizing my invention on a large scale is that when thereare many spots corresponding to Land ,8 signals, transniitted them any A will go, to thelnearest B,- or to several B's, de mi cg upon proximity and other causes. no method of obviating this difilcnlty is to use a given A only during a certain assigned time for communicating with a certain B the particular-B being, arranged to receive communications only during the assigned time. Thus, if there were ten Bs within a given area, then the first B might be .used vi'or the first hour, the second B for the next hour, and so on,.aud the first A for the first five minutesof the first hour, the second 'Aior the next five minntcs,and so on, so that sit-her one of the A's might hsve'i'ree communication with the first B, each for its assigned. time duringthe first hour, and either A with the second each for its assigned five minutes of the second hour, and so on.

In practice there will be of course both a 5 receiver and tra'nsmitterat A and B, proper switches being used to brin either intense, as will be well understood wi out description.

s amass I have spoken only of telephone-instruments, as these give the best results; but any electric instruments may be used capable of utilizing the currents passing .through 'the earth from 5 0 to 1),.nndthe strength of-snch 'n'urmnls can be largely increased by increasing the positive potential of C and the negative potential of D. It will also be obvious that if the end of coil G (shown in the diagram as I connected with 10 one armature of condenser-H) be grounded, and the end shown grounded be connected with the condenser, then C will be minus, and

- D must therefore be made plus.

What I claim is- The art above described of communicating r 5 by.electrieit-y, consisting in first establishing 

